The present invention relates to isomeric mixtures containing greater than 50% cis-2-methyl-3-pentenoic acid produced by, interalia, a number of processes and novel compositions using such mixtures of cis and trans isomers of 2-methyl-3-pentenoic acid to alter the flavor of foodstuffs, chewing gum and medicinal products.
There has been considerable work performed related to substances which can be used to impart (or enhance) flavors to (or in) various consumable materials, e.g., foodstuffs, medicinal products and chewing gums. These substances are used to diminish the use of natural materials, some of which may be in short supply and to provide more uniform properties in the finished product. Sweet, fruity, strawberry, winey-cognac, butter-like, rum-like, and butterscotch aromas as well as sweet, strawberry, nutty-coconut, fatty, butter-like, rum-like and butterscotch-like tastes are particularly desirable for many uses in foodstuff flavors, medicinal product flavors and chewing gum flavors.
U.S. Pat. No. 3,499,769 issued on Mar. 10, 1970 discloses processes for imparting a fresh fruity flavor (particularly strawberry flavor) to foods by adding a small amount of 2-methyl-2-pentenoic acid to the foodstuff. In U.S. Pat. No. 3,499,769 it is emphasized that the basic nuance imparted by 2-methyl-2-pentenoic acid is a "berry" flavor. Quite unexpectedly, the novel isomeric mixtures of the instant invention have properties different in kind from the 2-methyl-2-pentenoic acid of U.S. Pat. No. 3,499,769 which is only fruity and strawberry-like and does not have the sweet, fruity, butter-like, rum-like, and butterscotch aroma and taste qualities of the isomeric mixtures of the instant invention.
Other isomeric mixtures of 2-methyl-3-pentenoic acid are shown to be prepared by Boorman and Linstead, J. Chem. Soc. 1935, 258-67 (abstracted by Chem. Abstracts, Vol. 29, pages 2912 (7/8). 2-Ethyl-3-pentenoic acid is shown to be prepared by Fichter and Obladen, Berichte, 42, 4703-7 by distillation of alpha-ethyl gamma methyl paraconic acid which, in turn, is formed by reduction using a sodium-mercury amalgam of ethyl-alpha-ethyl aceto-succinate. The above-disclosed processes produce isomer mixtures which are considered to be different in kind insofar as their organoleptic properties are concerned from the isomer mixtures produced by the process of the instant invention.
Ethyl-2-methyl-3-pentenoate (95% 3:1 trans:cis isomer and 5% ethyl-2-methyl-2-pentenoate) has been offered as a development chemical by Toray Industries, Inc. of 2, Nihonbashi-Muromachi 2-chome, Chuo-Ku, Tokyo, Japan.
McGreer, et al, Can. J. Chem. 41, 726-31 (1963) discloses the production of various alkyl esters of pentenoic and butenoic acids by means of pyrolysis of 3,5-dimethyl-3-carbomethoxy .sup.1 -pyrazoline. Thus, on page 728 of the McGreer article, products having the following structures are shown to be produced: ##SPC1##
Tsuji, et al, J. Am. Chem. Soc., 86, (20) 4350-3 (1964) discloses the production of alkyl alkenoates by means of reaction of carbon monoxide, alkenyl halides and alkanols with use of palladium chloride as a catalyst. Other methods for the synthesis of alkyl alkenoates are set forth in the following references:
i. French Patent No. 1,398,856, issued February 19, 1965;
ii. Brewis and Hughes, Chem. Communications, (8), 157-8 (1965);
iii. Bordenca and Marsico, Tetrahedron Letters (16), 1541-3 (1967); and
iv. Hosaka and Tsuji, Tetrahedron, 27, (16) 3821-9 (1971).
None of the above references sets forth a process for preparing the cis isomer of an alkyl pentenoic acid or mixtures containing more than 50% cis isomer.
Felkin, et al, Ann. Chem. (Paris) 6 (1), 17-26 (1971) discloses processes for producing high cis and high trans 2-methyl-3-pentenoic acid and methyl-2-methyl-3-pentenoate mixtures, according to the following reaction sequences: ##SPC2##
A process for preparing the high cis acid mixture is set forth in Felkin, et al, Chemical Communications, No. 802, pages 75 and 76 (Dec. 29, 1965).